[0.31.0-rc] Enable to perform transform on the first argument of pipe method

[chimame]

First of all, I really like the library called valibot. I'm grateful to them for providing such a great library.

Overview

Reproduce the behavior of the coerce method with the pipe method

Details

The coerce method will be removed in 0.31.0. Therefore, I think that migrating the coerce method will be as follows, as written in the documentation.

describe('sample', () => {
  it('should throw an error when the string is empty', () => {
    // When using version 0.30.0 of valibot
    // const schema = coerce(string(), (value) => value === '' ? undefined : value)
    // When using version 0.31.0-rc.1 of valibot
    const schema = pipe(string(), transform((value) => value === '' ? undefined : value))

    const result = safeParse(schema, '')
    expect(result.success).toBe(false)
  })
})

However, in the case of the coerce method, the transformation is performed before verification, so I believe that the correct migration behavior will match the coerce method if you can pass the transform to the first argument of the pipe method.

const schema = pipe(transform((value) => value === '' ? undefined : value), string())

With the current implementation, it seems possible to execute it as long as you ignore the type. Please let me know if the migration method to 0.31.0 is incorrect.

[fabian-hiller]

The coerce method has been removed because I felt it was an insecure API. In most cases, you don't want to coerce an unknown input into a specific data type. Instead, you want to transform a specific data type into another specific data type. For example, a string or a number into a date. To explicitly define the input type, we recommend using the new pipe method together with the transform action to achieve the same functionality.

// Before
const DateSchema = v.coerce(v.date(), (input) => new Date(input));

// After
const DateSchema = v.pipe(
  v.union([v.string(), v.number()]), // <-- Select which input types to accept
  v.transform((input) => new Date(input))
);

You can also accept unknown to have the same behavior as with the older versions.

const DateSchema = v.pipe(
  v.unknown()
  v.transform((input) => new Date(input))
);

[chimame]

I always appreciate a quick response. Using unknown is a good workaround. I modified the code I presented in this way to get the expected behavior.

describe('sample', () => {
  it('should throw an error when the string is empty', () => {
    // When using version 0.30.0 of valibot
    // const schema = coerce(string(), (value) => value === '' ? undefined : value)
    // When using version 0.31.0-rc.1 of valibot
    const schema = pipe(unknown(), transform((value) => value === '' ? undefined : value), string())

    const result = safeParse(schema, '')
    expect(result.success).toBe(false)
  })
})

I will modify my library based on this code. Thank you so much for your response. I hope Valibot, a great library, will be more widely adopted.